Biogas typically refers to a gas produced by the biological breakdown of organic matter in the absence of oxygen. It is comprised primarily of methane and carbon dioxide. It can be combusted with oxygen and the energy release allows biogas to be used as a fuel. Considered a renewable fuel and electricity produced from it can be used to attract renewable energy subsidies in some parts of the world.

Pacific Gas and Electric (PG&E) last year announced an agreement with BioEnergy Solutions, a Central Valley waste-to-energy company, to deliver renewable energy to PG&E's customers. Under the agreement, BioEnergy Solutions would deliver up to three billion cubic feet of renewable natural gas a year to PG&E, enough to meet the electricity needs of approximately 50,000 PG&E residential customers.

Now the utility says that the manure-powered pipeline project has officially been turned on, and is producing commercial-grade, renewable natural gas, or biogas, produced when microbes break down a methane-rich source like manure. So-called cow power projects, entail placing manure from farms into covered lagoons that will trap the gas as the manure decomposes.

The project, approved by the California Public Utilities Commission (CPUC), is the first in the state to deliver that level of pipeline-quality, biogas to a utility. PG&E has been working to make sure it can meet the state mandate to deliver 20 percent of its electricity via clean sources by 2010. While biogas is just a portion of that portfolio, which also includes sources like solar and geothermal, biogas is significant — the utility is also working with biogas builder Microgy to complete this task. Biogas can not only produce clean energy, it can also help make farming more sustainable, by making the manure useful. Here’s to a win-win proposal for not-so-clean clean energy!